"… are required to change the motion of the 5 1/8 ounce ball from a speed of 90 mph …."

145 g

Author's measurement of a Wilson Baseball (Model A1001).

"142.54 g"

142.54 g

Baseball was invented around the last quarter of the 1800s. In the game of
baseball, we all know that the ball is the main object in the game. A baseball
is a small, round, and hard. The weight of a baseball must be between 5
and 5 ¼ ounces (142 to 149 grams) and its circumference from
9 to 9 ¼ inches (22.9 to 23.5 centimeters).

The formation of the ball begins with a ½ ounce (14 g), 2.9 inch
(7.4 cm) diameter cork core. A layer of black rubber is then applied followed
by a layer of red rubber each weighing ⅞ of an ounce (25 g). Afterwards,
121 yards (111 m) of blue-gray wool followed by 45 yards (41 m)
of white wool yarn are added to the outside. The ball is then wrapped
in cowhide covering held together by 216 stitches and some rubber cement.
Red stitches are placed on the ball to allow pitchers to throw curve balls.
Curve balls curve since the air resistance on the stitches is non-uniform.

From my experiment of weighing a baseball, the result came out to be 142.54 grams
which fits within the accepted range of 142 to 149 grams.